Liming, Fertilizer and Harvest Decisions in an Acid Red-Soil Mulberry Plot
A farmer in a red lateritic belt has 0.4 ha of four-year-old mulberry (variety S-1635) planted at 90 cm × 90 cm. A soil test shows pH 5.3, organic carbon 0.31%, available nitrogen 180 kg/ha (low), phosphorus 12 kg/ha (low) and potassium 95 kg/ha (medium). Leaves are pale yellow with green veins, new shoots are short, and about 30% of leaves have brown spots with grey centres. The farmer irrigates every seven days with borewell water of EC 1.8 dS/m and has applied 100 kg urea/ha in two splits, but no farmyard manure or lime. The last pruning was in December and a harvest is due in 45 days. The farmer plans to apply more urea and to strip all leaves at once for a 100-dfl rearing. Labour is available and farmyard manure can be arranged locally. Advise the farmer.
1. Diagnose the likely soil and leaf problems and state the amendment plan before the next crop, including why lime and FYM are needed.
Read the worked answer
The pale yellow leaves with green veins, low organic carbon and low available N point to nitrogen deficiency, but pH 5.3 is the root constraint: at that acidity phosphorus is less available and added urea will give a poor response. Brown spots with grey centres suggest a leaf-spot disease favoured by poor nutrition and humid foliage. Do not simply add more urea. Apply agricultural lime according to the soil-test lime requirement; for a pH 5.3 red soil a common guide is about 2 t/ha, but the laboratory recommendation should be followed. Incorporate 20–25 t/ha well-rotted FYM before the next pruning. Correct P and K with a soil-test-based basal dose and split N into three or four doses. Remove and destroy badly spotted leaves. Re-test pH after the crop so that the next lime dose is based on evidence, not habit.
2. Prepare a practical irrigation and fertilizer schedule for the 0.4 ha plot that avoids salinity risk from the borewell water.
Read the worked answer
Borewell water at EC 1.8 dS/m is marginal for mulberry, so the aim is to meet crop demand without building up salt. Irrigate at 5–7-day intervals according to soil moisture, wetting the root zone fully but avoiding standing water. Mulch with 5–7 cm of straw or FYM to reduce evaporation and salt accumulation at the surface. If a white salt crust appears, give one heavier leaching irrigation and improve drainage. Apply fertilizer in split doses after irrigation, never on dry soil. Calculate the plot dose from the per-hectare recommendation and divide it into four or five applications; for a 0.4 ha plot, a 100 kg N/ha recommendation becomes 40 kg N for the plot. Keep lime and ammonium fertilizers in separate applications, with lime applied two to three weeks before FYM or fertilizer.
3. How should the farmer harvest and prune to protect leaf quality and the next crop?
Read the worked answer
The farmer should not strip all leaves at once before a 100-dfl rearing. Harvest mature leaves from the lower and middle branches first, leaving the top four to six leaves and the growing tip to maintain photosynthesis. Match leaf type to larval stage: tender top leaves for young larvae, mature leaves for late-age larvae. This reduces digestive upset and flacherie risk. After harvest, prune at the recommended height above ground and apply FYM plus fertilizer immediately to stimulate the next flush. Harvest in the morning or late afternoon, carry leaves in shaded baskets and feed them within a few hours. Keep young-larva and late-age leaf lots separate. If the whole plot is stripped now, the next crop will be delayed and the plants will be weakened.